1. Field of the Invention
This invention relates to use of mesoionic 1,2,4-triazolium-3-thiolates as silver halide stabilizers and fixing agents. Such compounds are useful in stabilizing and fixing a developed image in a heat developable and heat stabilizable photographic silver halide material and process. It also relates to use of such stabilizers and fixing agents in photographic silver halide processing compositions.
2. Description of the State of the Art
Mesoionic sulfur containing tetrazole compounds have been described in the photographic art as photographic additives to improve image tone and density in, for instance, U.S. Pat. No. 4,003,910. However, the prior art does not suggest that these compounds would be useful in a heat developable and heat stabilizable photographic material and process, nor as silver halide stabilizers and fixing agents.
The use of stabilizers and stabilizer percursors in heat developable and heat stabilizable photographic materials and processes is known. Examples of known stabilizers and stabilizer precursors are described in, for instance, U.S. Pat. No. 4,012,260. An example of a heterocyclic stabilizer precursor is 2-amino-2-thiazolinium trichloroacetate.
A continuing need has existed for water-soluble, organic stabilizers and fixing agents for photographic silver halide that provide light-insensitive silver (I) complexes upon exposure and processing of a photographic silver halide material, such as a heat developable and heat stabilizable material comprising a silver halide stabilizer. Such light-insensitive silver (I) complexes help provide light stability to a developed image in a processed photographic silver halide element.
The term "material", as used herein, such as in photographic silver halide material, refers to photographic elements and photographic compositions. For instance, the term "heat developable and heat stabilizable photographic silver halide material" refers to photographic elements and photographic compositions.